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Attack Rate (attack + rate)
Selected AbstractsThe invasive alien leaf miner Cameraria ohridella and the native tree Acer pseudoplatanus: a fatal attraction?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2010Christelle Péré 1The horse-chestnut leaf miner Cameraria ohridella is an invasive moth in Europe and a serious pest of horse-chestnut Aesculus hippocastanum. The moth also occasionally attacks sycamore maple Acer pseudoplatanus, when situated beside infested horse-chestnuts. 2The main objective of the present study was to provide an overview of the relationship between C. ohridella and A. pseudoplatanus and to determine whether C. ohridella has the potential to shift to this native tree. 3In the field, females oviposit on different deciduous tree species. Although less frequently attacked than A. hippocastanum, A. pseudoplatanus was clearly preferred for oviposition over 12 other woody species investigated. 4Surveys in Europe demonstrated that the majority of A. pseudoplatanus trees found beside infested A. hippocastanum had mines of C. ohridella, even though more than 70% of the larvae died within the first two instars. Attack rates and development success greatly varied from site to site. Attack levels on A. pseudoplatanus were not always correlated with those on A. hippocastanum, and mines on A. pseudoplatanus were sometimes observed beside weakly-infested A. hippocastanum. 5Field observations, experimental exposure of A. pseudoplatanus saplings and rearing trials in a common garden study showed that individual trees may vary in their susceptibility to C. ohridella, whereas there was no evidence that C. ohridella populations vary in their performance on A. pseudoplatanus. 6To date, there is little evidence that C. ohridella represents a major risk for A. pseudoplatanus. [source] Long-term effects of ungulates on phytophagous insectsECOLOGICAL ENTOMOLOGY, Issue 2 2007JOSÉ M. GÓMEZ Abstract 1.,Most plants interact with a diverse suite of herbivores, allowing the opportunity for the existence of positive and negative interactions between highly dissimilar organisms. However, most studies on herbivorous interactions have been performed under the assumption that they occur mainly between similar species. Consequently, ecologists are still far from a full understanding of the ecological factors that determine insect population dynamics. 2.,In this study, a 7-year field experiment was conducted that manipulated the presence of ungulates to evaluate their effects on the abundance, attack rate, and survival of four guilds of co-occurring herbivorous insects living on the same host plant: seed predators, stem borers, gall makers and sap suckers. These four guilds differed in habits and behaviour, the first three being sessile and endophytic and the last being free-living. 3.,This study shows that the abundance of all four guilds was negatively affected by ungulates. However, the effect on attack rate differed among guilds, as mammals do not affect the seed predator attack rate. Ungulates also differentially affected insect survival, ingesting only seed predators and gall makers. 4.,In summary, this study suggests that diverse mechanisms may affect different insect guilds in different ways. Therefore, competition between disparate herbivores appears to be complex and can be provoked by multiple mechanisms. [source] Interspecific interference and the functional response of four species of carnivorous stonefliesFRESHWATER BIOLOGY, Issue 9 2003J.M. Elliott Summary 1.,A previous study compared the functional responses to their prey and intraspecific interference in mature larvae of Perlodes microcephalus, Isoperla grammatica, Dinocras cephalotes and Perla bipunctata. The present study extends this work by assessing interspecific interference between pairs of these species in equal numbers (one, two or three larvae per species) to provide total predator densities of two, four or six larvae. Baetis larvae as prey were replaced as they were eaten, and their density per predator was varied between 20 and 200 larvae. 2.,The number of prey eaten by each competing species increased curvilinearly with prey density, the relationship being well described by a Type II model. Of the two constants in the model, handling time varied considerably between species, mean values being shortest for Perlodes, slightly higher for Isoperla, and much higher for Dinocras and Perla. It was not affected significantly either by predator density or the identity of the competing species. 3.,Attack rate also varied between species and decreased with predator density. This decrease was slight for Perlodes, and also for Dinocras and Perla in competition with Isoperla. The decrease in Dinocras and Perla was similar to that for intraspecific interference. 4.,The decrease in attack rate was described by a convex curve for Perlodes with the other three species and for Dinocras/Perla with Isoperla, but by a concave curve (negative power function) for Isoperla competing with the other three species, and for both Dinocras and Perla in competition with Perlodes. Prey consumption also decreased with predator density, the severity of competition with different species reflecting that for attack rate. 5.,A comparison with previous results for intraspecific interference showed that the latter was dominant for Perlodes in all contests and for Dinocras or Perla competing with Isoperla, whilst interspecific interference dominated for Isoperla in all contests and for Dinocras and Perla competing with Perlodes. Both types of interference were applicable to competition between Dinocras and Perla. Isoperla was the least, and Perlodes the most, aggressive of the four species with Dinocras and Perla intermediate. [source] How starvation risk in Redshanks Tringa totanus results in predation mortality from Sparrowhawks Accipiter nisusIBIS, Issue 2008WILL CRESSWELL Redshanks Tringa totanus that are preyed upon by Sparrowhawks Accipiter nisus at the Tyninghame Estuary, Firth of Forth, Scotland, provide an example of how the starvation,predation risk trade-off results in mortality. In this trade-off, animals cannot always optimize anti-predation behaviour because anti-predation behaviours, such as avoiding predators, are usually incompatible with foraging behaviours that might maximize intake rates. Therefore, as animals compensate for starvation risk, predation risk increases. Sparrowhawks are the main direct cause of death in Redshanks at Tyninghame. Sparrowhawk attack rate is determined by Redshank vulnerability, and vulnerability decreases as group size and distance to cover increase, and probably as spacing decreases. But reduction of predation vulnerability reduces feeding rate because areas away from cover are less food-profitable and grouping results in increased interference competition. Increased starvation risk in midwinter means Redshanks are forced to feed on highly profitable prey, Orchestia amphipods, the behaviour of which means that Redshanks are forced to feed vulnerably, in widely spaced groups, close to predator-concealing cover. Therefore, it is the constraints that limit the ability of Redshanks to feed in large, dense flocks away from cover that ultimately lead to mortality. We investigate this hypothesis further by testing the prediction that mortality can be predicted directly by cold weather and population density. We demonstrate that the overall number of Redshanks and the proportion of Redshanks killed increase in cold months when controlling for population size. We also demonstrate that the proportion of Redshanks killed increases when there are fewer Redshanks present, because the success rate of hunting Sparrowhawks increases, probably because effective management of predation risk through flocking is constrained by a low population size. Redshanks therefore provide an example of how directly mortality caused by predation arises from starvation risk and other constraints that prevent animals from optimizing anti-predation behaviour. [source] The use of oseltamivir during an influenza B outbreak in a chronic care hospitalINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 1 2009Holly Seale Background, Residents of nursing homes and long-term care facilities are at a higher risk of outbreaks of influenza and of serious complications of influenza than those in the community. In late July 2005, a 90-bed chronic care psycho-geriatric hospital in Sydney, Australia, reported cases of influenza-like illness (ILI) occurring amongst its residents. Methods, An investigation to confirm the outbreak, and its cause, was undertaken. Influenza vaccination levels amongst residents, and the effects of antiviral drugs used for prevention and treatment, were assessed. Oseltamivir was only given to the residents, in the form of both treatment and prophylaxis. Results, A total of 22 out of 89 residents met the clinical case definition of ILI with onset on or after 27 July 2005. This represents an attack rate of 25%. Oseltamivir was commenced on day 9 of the outbreak. Influenza B was identified in six residents as the causative agent of the outbreak. No deaths or acute hospitalization were recorded for this outbreak and there were no further reported cases after the introduction of oseltamivir. Vaccine effectiveness was 75% and the strain of influenza B isolated was well matched to that year's vaccine. Conclusions, There are few data on the use of oseltamivir in influenza B outbreaks. Early antiviral intervention appeared to curtail this outbreak of influenza B in a chronic care facility. We found high vaccine effectiveness in this frail, institutionalized population, highlighting the importance of influenza vaccination for residents of chronic care facilities. [source] Effect of experimentally altered food abundance on fat reserves of wintering birdsJOURNAL OF ANIMAL ECOLOGY, Issue 5 2003Christopher M. Rogers Summary 1Current models of adaptive fat regulation make opposing predictions concerning the effect of increased winter food supply on size of the avian winter fat reserve. To distinguish between models, food supply was varied experimentally in nature and two measures of size of the fat reserve were taken at food-supplemented sites and non-supplemented sites. 2In two winters, most of the seven species sampled showed slightly higher visible subcutaneous fat class at supplemented than at non-supplemented sites; treatment and species factors were statistically significant. Body mass corrected for wing length showed a similar if non-significant trend. 3A parallel dispersal study of birds colour-banded at non-supplemented sites showed that these birds did not move 0·8 or 1·5 km to use supplemental food at private feeding stations in the study areas. In addition, accipiter hawk attack rate did not differ between supplemented and non-supplemented sites. 4These results are consistent with a model of adaptive fat regulation (based on between-day environmental variability caused by severe weather events) that predicts an increase in the winter fat reserve at increased food supply. Other published studies, all from the north temperate zone, showed the same pattern. 5The present results are inconsistent with a second model (based on within-day foraging interruption) which predicts a decrease in the fat reserve under increased food supply. However, a set of published studies, all from tropical regions or regions with mild maritime climate, showed the decrease at higher food predicted by the second but not the first model. 6Models of adaptive fat regulation in small birds are therefore limited in their predictive power, perhaps because they are developed for environments that differ in the time scale of environmental stochasticity. New studies are needed that explore further the complexities of environment-specific adaptive fat models, e.g. a winter feeding experiment in a tropical bird species. [source] Functional response of Neoseiulus californicus (Acari: Phytoseiidae) to Tetranychus urticae (Acari: Tetranychidae) on strawberry leavesJOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2010J. J. Ahn Abstract Neoseiulus californicus (McGregor) is a predatory mite employed for biological control of the agricultural pest Tetranychus urticae (Koch). We explored whether environmental differences, in this case the trichome densities of abaxial leaf surfaces of strawberry cultivars (,Maehyang' and ,Sulhyang' varieties) affect the functional response of adult female N. californicus preying on immature stages (egg, larva and nymph) of T. urticae. We also evaluated the functional response of N. californicus to eggs of T. urticae at different temperatures (15, 20, 25, 30 and 35°C). We conducted a logistic regression of the proportion of prey consumed as a function of initial prey density to identify functional response types, and used nonlinear least-squares regression and the random predator equation to estimate attack rates and handling times. The functional response of adult female N. californicus to T. urticae was not influenced by non-glandular trichomes on abaxial leaves but was affected by temperature. Overall, adult female N. californicus exhibited a type 2 functional response to T. urticae. The handling time of N. californicus was highest (1.9970 h) against T. urticae nymphs. The attack rate did not change much at 15,30°C, but was significantly higher at 35°C. The handling time decreased significantly with increasing temperature at 15,35°C. At 35°C, the attack rate was highest (0.2087) and the handling time was lowest (0.9511 h). [source] Functional response of Picromerus bidens: effects of host plantJOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2007K. Mahdian Abstract:, The influence of three solanaceous plants (tomato, sweet pepper and eggplant) on the functional response of the predatory bug Picromerus bidens to densities of fourth-instar larvae of the beet armyworm Spodoptera exigua was assessed. Logistic regression indicated a type II functional response on all host plants. Over all prey densities, P. bidens killed significantly fewer fourth instars of S. exigua on tomato than on sweet pepper or eggplant (1.96 ± 0.17 vs. 4.37 ± 0.19 and 3.90 ± 0.15 larvae per predator per 24 h respectively). A higher theoretical maximum predation rate was estimated on sweet pepper (11.1 prey larvae per day) and eggplant (7.4) than on tomato (5.4). The mean number of prey killed per day by P. bidens females ranged from 0.78 at a density of one prey on tomato to 8.45 at a density of 24 prey on sweet pepper. The data indicated that the estimates of handling time (Th) and attack rate (a) were highly affected by host plant. Based on asymptotic 95% confidence intervals, a lower attack coefficient was found on tomato (0.02 h,1) than on sweet pepper or eggplant (0.07 and 0.11 h,1 respectively). On the other hand, handling times were significantly longer on tomato (4.42 h) and eggplant (3.23 h) than on sweet pepper (2.15 h). This laboratory study suggests that plant characteristics influence the ability of P. bidens to respond to changes in prey density. [source] Population density affects foraging behavior of male Black-throated Blue Warblers during the breeding seasonJOURNAL OF FIELD ORNITHOLOGY, Issue 2 2007Robert C. Dobbs ABSTRACT Foraging behavior often reflects food availability, a resource that may increasingly limit breeding birds as intraspecific crowding increases. Measuring foraging behavior, therefore, provides a way to investigate effects of population density on food limitation, an important link in understanding how crowding functions to regulate populations. We quantified three components of foraging behavior (prey attack rate, foraging speed, and relative use of morphologically constrained attack maneuvers) for male Black-throated Blue Warblers (Dendroica caerulescens) breeding under experimentally manipulated density conditions. Building on the previous work showing the density of conspecific neighbors affects territory size, reproductive success, and the time budgets of males (Sillett et al. 2004, Ecology 85: 2467,2477), we further show that density affects male foraging strategies. Although not differing in attack rate or foraging speed, male Black-throated Blue Warblers on territories with reduced neighbor densities used energetically expensive aerial attack maneuvers significantly less frequently than males in control (high-density) territories during both the incubation period and when provisioning nestlings and fledglings. We conclude that males altered their foraging behavior to compensate for density-related reductions in time available for foraging and that population density may constrain the time available for foraging. SINOPSIS La conducta de forrajeo muchas veces refleja la disponibilidad de alimentos, un recurso que puede limitar la capacidad reproductiva con el aumento en el número de individuos. El medir la conducta de forrajeo, puede proveer de una forma de investigar el efecto de la limitación de alimentos en la dencidad poblacional, enlace importante para entender como el acinamiento funciona para regular una población. Cuantificamos tres componentes de la conducta de forrajeo (tasa de ataque de la presa, velocidad de forrajeo, y uso relativo de maniobras de ataque con respecto a restricciones morfológicas) para machos de Dendroica caerulescens reproduciéndose bajo densidades manipuladas experimentalmente. Utilizando como base trabajos que señalan que la densidad conespecífica vecinal afecta el tamaño del territorio, el éxito reproductivo y el presupuesto utilizado por los machos (Sillett et al. 2004, Ecology 85:2467-2477) demostramos que la densidad afecta además la estrategia de forrajeo de los machos. Aunque no hay diferencia en la tasa de ataque o velocidad de forrajeo, machos en territorios con pocos vecinos, utilizaron maniobras de forrajeo energéticamente más costosas y con una frecuencia significativamente menos costosa que el grupo control (áreas con alta densidad), tanto durante la fase de incubación como la de crianza de pichones. Concluimos que los machos alteran su conducta de forrajeo para compensar por la reducción en la densidad de individuos y en el tiempo disponible para forrajear, y que la densidad de la población puede limitar el tiempo disponible para forrajear. [source] Evidence of intrafamilial transmission of rotavirus in a birth cohort in South IndiaJOURNAL OF MEDICAL VIROLOGY, Issue 10 2008Indrani Banerjee Abstract Transmission of rotavirus infection was studied in a birth cohort of children based in an urban slum in Vellore and their familial contacts. Contemporaneous samples from index patients and their familial contacts were collected for analysis in three different settings. Firstly, samples were collected from familial contacts during a period of rotavirus infection in children from the cohort. Secondly, on occasions when a family member had rotavirus diarrhea, samples from the cohort child were taken for analysis. Lastly, asymptomatic surveillance samples collected at predetermined time points from both the cohort child and familial contacts were analyzed. From 560 samples collected from family members during symptomatic and asymptomatic rotavirus infections in these children, three rotavirus transmissions were identified, accounting for a secondary attack rate of 0.54%. In four instances of rotavirus diarrhea in a family member, one infection was transmitted to the cohort child. Nucleotide sequence and phylogenetic analysis demonstrated a high degree of similarity in all these pairs ranging between 99% and 100% at both the nucleotide and the deduced amino acid levels, highly suggestive of person-to-person transmission of rotavirus infection. There was complete concordance of rotavirus genotyping between these pairs. No transmission events were noted from 14 asymptomatic rotavirus infections identified during routine surveillance of family members. This study is the first to use phylogenetic analysis to study the intrafamilial spread of rotavirus infection. J. Med. Virol. 80:1858,1863, 2008. © 2008 Wiley-Liss, Inc. [source] Common Health Hazards in French Pilgrims During the Hajj of 2007: A Prospective Cohort StudyJOURNAL OF TRAVEL MEDICINE, Issue 6 2009Philippe Gautret MD Background. The majority of published studies on Hajj-related diseases were based on hospitalized patient cohorts. Methods. A total of 545 Hajj pilgrims from Marseille were enrolled in a prospective epidemiological study to evaluate the incidence of common health hazards. They were administered a questionnaire before traveling addressing demographic factors and health status indicators and a post-travel questionnaire about travel-associated diseases. Results. Respondents had a median age of 61 years and originated mainly from North Africa (81%). A significant proportion of individuals had chronic medical disorders such as walking disability (26%), diabetes mellitus (21%), and hypertension (21%). A total of 462 pilgrims were administered a questionnaire on returning home. A proportion of 59% of travelers presented at least one health problem during the pilgrimage and 44% of the cohort attended a doctor during travel; 3% were hospitalized. Cough was the main complaint among travelers (attack rate of 51%), followed by headache, heat stress, and fever. Few travelers suffered diarrhea and vomiting. Cardiovascular diseases, neurological disorders, trauma, skin and gastrointestinal problems were not frequently observed in our survey, suggesting that their prevalence among the causes of admission to Saudi hospitals reflects a bias of selection. Cough episodes were significantly more frequent in individuals >55 years. We also evidenced that women were more likely to present underlying chronic cardiovascular disorder and diabetes compared to men and that they more frequently suffered from cough episodes associated with fever during the Hajj. Conclusions. Health risks associated with the Hajj in our experience are much more related to crowding conditions than to travel. Our work suggests that the studies performed in Saudi specialized units probably overestimate the part of certain diseases within the spectrum of Hajj-associated diseases. Our results also suggest that old female Hajjes should be considered as a high-risk population and that preventive measures should be reinforced before departing for Saudi Arabia. [source] Travelers' Diarrhea in Children Visiting Tropical CountriesJOURNAL OF TRAVEL MEDICINE, Issue 1 2009Filipe Glória Silva MD We studied a group of 174 Portuguese children (aged 2 mo,16 y) who mostly traveled to tropical Portuguese-speaking countries and found an attack rate of 21.8% for travelers' diarrhea, much lower than previously described. We also showed that African rate analysis by region may hide significant differences between countries. [source] Malaria in Brazilian Military Personnel Deployed to AngolaJOURNAL OF TRAVEL MEDICINE, Issue 5 2000COL L. Jose Sanchez Background: Malaria represents one of the most important infectious disease threats to deployed military forces; most personnel from developed countries are nonimmune personnel and are at high risk of infection and clinical malaria. This is especially true for forces deployed to highly-endemic areas in Africa and Southeast Asia where drug-resistant malaria is common. Methods: We conducted an outbreak investigation of malaria cases in Angola where a total of 439 nonimmune Brazilian troops were deployed for a 6-month period in 1995,1996. A post-travel medical evaluation was also performed on 338 (77%) of the 439 soldiers upon return to Brazil. Questionnaire, medical record, thick/thin smear, and serum anti- Plasmodium falciparum antibody titer (by IFA) data were obtained. Peak serum mefloquine (M) and methylmefloquine (MM) metabolite levels were measured in a subsample of 66 soldiers (42 cases, 24 nonmalaria controls) who were taking weekly mefloquine prophylaxis (250 mg). Results: Seventy-eight cases of malaria occurred among the 439 personnel initially interviewed in Angola (attack rate = 18%). Four soldiers were hospitalized, and 3 subsequently died of cerebral malaria. Upon return to Brazil, 63 (19%) of 338 soldiers evaluated were documented to have had clinical symptoms and a diagnosis of malaria while in Angola. In addition, 37 (11%) asymptomatically infected individuals were detected upon return (< 1% parasitemia). Elevated, post-travel anti- P. falciparum IFA titers (, 1:64) were seen in 101 (35%) of 292 soldiers tested, and was associated with a prior history of malaria in-country (OR = 3.67, 95% CI 1.98,6.82, p < .001). Noncompliance with weekly mefloquine prophylaxis (250 mg) was associated with a malaria diagnosis in Angola (OR = 3.75, 95% CI 0.97,17.41, p = .03) but not with recent P. falciparum infection (by IFA titer). Mean peak levels (and ratios) of serum M and MM were also found to be lower in those who gave a history of malaria while in Angola. Conclusions: Malaria was a significant cause of morbidity among Brazilian Army military personnel deployed to Angola. Mefloquine prophylaxis appeared to protect soldiers from clinical, but not subclinical, P. falciparum infections. Mefloquine noncompliance and an erratic chemoprophylaxis prevention policy contributed to this large outbreak in nonimmune personnel. This report highlights the pressing need for development of newer, more efficacious and practical, prophylactic drug regimens that will reduce the malaria threat to military forces and travelers. [source] A Dengue Outbreak among Camp Participants in a Caribbean Island, 1995JOURNAL OF TRAVEL MEDICINE, Issue 2 2000Rob Lyerla Background: Dengue, a mosquito-transmitted viral disease, is a risk for visitors in tropical and subtropical areas. Several participants in a community-assistance program in Tortola, British Virgin Islands, in August, 1995, reported dengue-like symptoms either before or soon after leaving the island. Methods: We conducted a retrospective cohort study to determine the extent of the outbreak, risk factors for illness, and the proportion of inapparent infections. Program participants were interviewed by telephone or mail, and asked to submit a serum sample for dengue diagnosis. A clinically-diagnosed case of dengue was defined as a person with fever and two or more of the following: headache, retro-orbital pain, myalgia, arthralgia, rash, or hemorrhagic manifestations. Serum specimens were tested for virus isolation, polymerase chain reaction (PCR), plaque-reduction neutralization (PRNT) or anti-dengue IgM and IgG antibody. Results: Thirty-two (97%) of the 33 program participants responded; 21 of the 32 (66%) provided at least one serum sample for study. The median age was 17 years; 20 (62%) were women. Of 32 respondents, 22 (69%) met the clinical case definition for dengue: 15 of them (68%) had a positive IgM antibody response and 7 did not submit a serum sample. Dengue 1 virus (DEN-1) was identified by PCR in one case and all 11 positive PRNT results. No asymptomatic infections were identified. No respondent used effective mosquito repellent, and only 2 (6%) used bednets. Conclusion: A DEN-1 outbreak with a high attack rate (69%) occurred in a group of young short-term community aid workers. There were no asymptomatic infections documented. Participants' rare use of bednets or effective mosquito repellent highlights the importance of providing travelers to tropical areas with information about dengue fever and the recommended precautions to protect against infection. [source] Failure of inactivated influenza A vaccine to protect healthy children aged 6,24 monthsPEDIATRICS INTERNATIONAL, Issue 2 2004Taro Maeda AbstractBackground:,The efficacy of inactivated influenza vaccine in healthy infants and children younger than 24 months has not been confirmed. The aim of the present study was to determine the prophylactic effect of inactivated influenza vaccine against influenza A in healthy children aged 6,24 months. Methods:,Healthy infants and young children (6,24 months old) were immunized by subcutaneous injection of inactivated influenza vaccine before influenza seasons. Age matched children were randomly assigned as the control. These children were followed up from January to April in each year (2000, 2001 and 2002). The attack rates of influenza A infection was compared and statistically assessed. Results:,The attack rate of influenza A virus infection in the vaccine group and the control group were 14.8% (n = 27) vs 12.5% (n = 32) in 2000 (P = 0.526); 2.8% (n = 72) vs 7.2% (n = 69) in 2001 (P = 0.203); and 3.4% (n = 52) vs 8.9% (n = 56) in 2002 (P = 0.205). The attack rates of influenza A between the two groups were not significantly different. Conclusion:,Inactivated influenza vaccine did not reduce the attack rate of influenza A infection in 6,24 month old children. [source] Was the adult Victorian attack rate for pandemic influenza H1N1 2009 lower than expected?AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 4 2010Geoffry Mercer No abstract is available for this article. [source] A lower than expected adult Victorian community attack rate for pandemic (H1N1) 2009AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 3 2010Nathan Grills Abstract Objectives: To determine the community seropositivity of pandemic (H1N1) 2009 influenza in order to estimate immunity and the community attack rate. Methods: Selected clusters of participants (n=706) in the ,Victorian Health Monitor' (VHM), from whom blood samples were taken between August and October 2009, were tested opportunistically for antibodies to pandemic (H1N1) 2009 influenza virus. A titre of ,1:40 was chosen as the cut-off for recording seropositivity. The proportion (95% CI) of seropositive participants, aged 18 to <65 years of age, were computed for groups of census collection districts (CDs) across metropolitan Melbourne. Results: The observed pandemic (H1N1) 2009 seropositivity rates for all CDs tested in metropolitan Melbourne was 16.0% (95% CI:12.9-19.1%); in northern Melbourne subset was 14.4% (95% CI:12.4-16.3%); and in eastern subset was 16.2% (95% CI:9.7-22.6%). The pre-pandemic (H1N1) 2009 positivity rate was estimated at 6%. Conclusion: Given this study's estimate of 16.0% seropositivity in adults in metropolitan Melbourne, and given the WHO laboratory's estimate of 6% pre-pandemic positivity, the estimated adult community attack rate was 10% for metropolitan Melbourne. Implications: This community attack rate is lower than anticipated and suggests that levels of immunity to Pandemic (H1N1) 2009 might be lower than anticipated. Although limited by a low response rate of 34%, this study suggests low adult seropositivity, which may be useful for public health professionals when encouraging the community to get vaccinated. [source] Gall size determines the structure of the Rabdophaga strobiloides host,parasitoid communityECOLOGICAL ENTOMOLOGY, Issue 5 2003Brian H. Van Hezewijk Abstract., 1.,The relationship between gall size and mortality of the willow pinecone gall midge Rabdophaga strobiloides (Diptera: Cecidomyiidae) was examined by determining the fate of all galls in a 30-ha area in central Alberta, Canada over 4 years. It was found that gall size has a large effect on the type and intensity of mortality experienced by the gall midge, and consequently this factor has the potential to influence the dynamics of the host,parasitoid interaction through the creation of phenotypic refuges. 2.,Total midge mortality ranged from 51% to 78% over the course of the study and was dominated by parasitism by Torymus cecidomyiae (Hymenoptera: Torymidae) and Gastrancistrus sp. (Hymenoptera: Pteromalidae) as well as predation by birds. Gall size had a strong, non-linear effect on the attack rates of each of these natural enemies. 3.,Birds attacked the smallest size classes. Torymus cecidomyiae preferentially attacked medium diameter galls and thus avoided predation by birds in smaller galls. Gastrancistrus sp. preferentially attacked the largest galls and consequently suffered lower rates of predation by both T. cecidomyiae and birds. 4.,This study emphasises the importance of understanding the interactions among mortality factors in order to describe adequately the susceptibility of R. strobiloides to parasitism and predation, and ultimately its population dynamics. [source] Refuge-mediated apparent competition in plant,consumer interactionsECOLOGY LETTERS, Issue 1 2010John L. Orrock Abstract At the intersection of consumer behaviour and plant competition is the concept of refuge-mediated apparent competition: an indirect interaction whereby plants provide a refuge for a shared consumer, subsequently increasing consumer pressure on another plant species. Here, we use a simple model and empirical examples to develop and illustrate the concept of refuge-mediated apparent competition. We find that the likelihood that an inferior competitor will succeed via refuge-mediated apparent competition is greater when competitors have similar resource requirements and when consumers exhibit a strong response to the refuge and high attack rates on the superior competitor. Refuge-mediated apparent competition may create an emergent Allee effect, such that a species invades only if it is sufficiently abundant to alter consumer impact on resident species. This indirect interaction may help explain unresolved patterns observed in biological invasion, such as the different physical structure of invasive exotic plants, the lag phase, and the failure of restoration efforts. Given the ubiquity of refuge-seeking behaviour by consumers and the ability of consumers to alter the outcome of direct competition among plants, refuge-mediated apparent competition may be an underappreciated mechanism affecting the composition and diversity of plant communities. Ecology Letters (2010) 13: 11,20 [source] Effects of parasitoid fecundity and host resistance on indirect interactions among hosts sharing a parasitoidECOLOGY LETTERS, Issue 6 2003George E. Heimpel Abstract We examine the effects of fecundity-limited attack rates and resistance of hosts to parasitism on the dynamics of two-host,one-parasitoid systems. We focus primarily on the situation where one parasitoid species attacks two host species that differ in their suitability for parasitism. While all eggs allocated to suitable hosts develop into adult parasitoids, some of the eggs allocated to marginal host do not develop. Marginal hosts can therefore act as a sink for parasitoid eggs. Three-species coexistence is favoured by low levels of parasitoid fecundity and by low levels of suitability of the marginal host. Our model also produces an indirect (+, ,) interaction in which the suitable host can benefit from the presence of the marginal host, but the marginal host suffers from the presence of the suitable host. The mechanism driving the indirect (+, ,) interaction is egg limitation of parasitoids incurred by allocating eggs to marginal hosts. [source] Diadegma mollipla parasitizing Plutella xylostella: host instar preference and suitabilityENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Robert S. Nofemela Abstract Oviposition decisions (i.e., host selection and sex allocation) of female parasitoids are expected to correspond with host quality, as their offspring fitness is dependent on the amount and quality of resources provided by a single host. The host size model assumes that host quality is a linear function of host size, with larger hosts believed to contain a greater quantity of resources, and thus be more profitable than smaller hosts. We tested this assertion in the laboratory on a solitary larval,pupal parasitoid Diadegma mollipla (Holmgren) (Hymenoptera: Ichneumonidae) developing on three instars (second,fourth) of one of its hosts, the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). In a no-choice test, parasitism levels and sex ratio (i.e., proportion of female progeny) were significantly high in hosts attacked in the second instar followed by third then fourth instars. However, the few parasitoids that completed a generation from the fourth instars did so significantly faster than conspecifics that started development in the other two instars. In direct observations, however, the parasitoids (i) randomly attacked the various host instars, (ii) spent a similar period examining the various host instars with their ovipositors, (iii) subdued all three host instars with about the same effort, and (iv) no statistical differences were observed in the attack rates on the three host instars. In a choice test, the females parasitized significantly more third instars followed by second then fourth instars. However, total parasitism in this experiment was 43% lower compared to parasitism of only second instars in the no-choice test. No significant differences were detected in progeny sex ratios. In both choice and no-choice tests, significantly more fourth instars died during the course of the experiments than second instars, while third instars were intermediate. The higher parasitism of third than second instars in the choice test indicates that the females perceived larger hosts as higher quality than smaller hosts, despite their lower suitability for larval development. [source] Multiparasitism of Choristoneura fumiferana by the ichneumonid Tranosema rostrale and the tachinid Actia interrupta: occurrence in the field and outcome of competition under laboratory conditionsENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2002Michel Cusson Abstract Tranosema rostrale (Brishke) (Hymenoptera, Ichneumonidae) and Actia interrupta Curran (Hymenoptera: Tachinidae) are the two endoparasitoids most frequently encountered in low-density populations of the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera, Tortricidae), in the Quebec City region. Monitoring of attack rates of implanted C. fumiferana larvae at two different study sites suggested the possible existence of competition between the two parasitoids, with A. interrupta seemingly displacing T. rostrale. Here, we show that multiparasitism involving these two species does occur in the field, but at a frequency too low to explain the seasonal pattern of decline in apparent parasitism by T. rostrale that accompanies the rise of A. interrupta attack rates. We also provide preliminary evidence, from laboratory experiments, that A. interrupta has a competitive advantage over T. rostrale and that the success of parasitism by A. interrupta may be enhanced by prior parasitism by T. rostrale under certain conditions, possibly due to the presence of the latter species' polydnavirus. In addition, we describe a PCR-based method that we developed to help detect the presence of T. rostrale eggs which often escape detection by simple visual examination of the dissected host larvae; DNA sequences specific to the polydnavirus injected by the female wasp at the time of oviposition can be readily amplified from whole host larvae. [source] Olfactory information saves venom during prey-capture of the hunting spider Cupiennius salei (Araneae: Ctenidae)FUNCTIONAL ECOLOGY, Issue 2 2006S. HOSTETTLER Summary 1The Neotropical spider Cupiennius salei Keyserling (Ctenidae) selects prey in a manner consistent with the amount of venom available in its venom glands. It distinguishes the venom sensitivity of different prey species, and uses its venom economically (according to the venom-optimization hypothesis). 2A prey-choice experiment was performed to test whether spiders use olfactory cues to detect prey and select prey items that are appropriate for their amount of available venom. 3The spider could choose between two similar prey dummies made of agar. We added the odour of two prey species, either by adding minced insects to an agar block or by offering it on filter paper which had previously been exposed to the living prey. Cupiennius salei spiders had either full or emptied venom glands. 4Two insects of distinctive venom sensitivity, but high acceptance, were tested: a sensitive cricket and a less sensitive cockroach. 5Using video surveillance, we found an attraction effect of prey odour in the prey-capture behaviour of C. salei. Spiders preferred agar pieces with minced insects or insect odour on filter paper over non-smelling items. Reaction frequency and attack rates were equal for spiders with full venom glands if they had to choose between cricket and cockroach odour. When the venom glands were empty, however, C. salei significantly preferred the venom-sensitive cricket over the venom-insensitive cockroach. 6We showed for the first time that C. salei uses its olfactory sense to detect prey items, and distinguishes between prey species with low and high sensitivity to spider venom. This study supports the venom-optimization hypothesis. [source] Dynamic versus static models in cost-effectiveness analyses of anti-viral drug therapy to mitigate an influenza pandemicHEALTH ECONOMICS, Issue 5 2010Anna K. Lugnér Abstract Conventional (static) models used in health economics implicitly assume that the probability of disease exposure is constant over time and unaffected by interventions. For transmissible infectious diseases this is not realistic and another class of models is required, so-called dynamic models. This study aims to examine the differences between one dynamic and one static model, estimating the effects of therapeutic treatment with antiviral (AV) drugs during an influenza pandemic in the Netherlands. Specifically, we focus on the sensitivity of the cost-effectiveness ratios to model choice, to the assumed drug coverage, and to the value of several epidemiological factors. Therapeutic use of AV-drugs is cost-effective compared with non-intervention, irrespective of which model approach is chosen. The findings further show that: (1) the cost-effectiveness ratio according to the static model is insensitive to the size of a pandemic, whereas the ratio according to the dynamic model increases with the size of a pandemic; (2) according to the dynamic model, the cost per infection and the life-years gained per treatment are not constant but depend on the proportion of cases that are treated; and (3) the age-specific clinical attack rates affect the sensitivity of cost-effectiveness ratio to model choice. Copyright © 2009 John Wiley & Sons, Ltd. [source] Functional response of Neoseiulus californicus (Acari: Phytoseiidae) to Tetranychus urticae (Acari: Tetranychidae) on strawberry leavesJOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2010J. J. Ahn Abstract Neoseiulus californicus (McGregor) is a predatory mite employed for biological control of the agricultural pest Tetranychus urticae (Koch). We explored whether environmental differences, in this case the trichome densities of abaxial leaf surfaces of strawberry cultivars (,Maehyang' and ,Sulhyang' varieties) affect the functional response of adult female N. californicus preying on immature stages (egg, larva and nymph) of T. urticae. We also evaluated the functional response of N. californicus to eggs of T. urticae at different temperatures (15, 20, 25, 30 and 35°C). We conducted a logistic regression of the proportion of prey consumed as a function of initial prey density to identify functional response types, and used nonlinear least-squares regression and the random predator equation to estimate attack rates and handling times. The functional response of adult female N. californicus to T. urticae was not influenced by non-glandular trichomes on abaxial leaves but was affected by temperature. Overall, adult female N. californicus exhibited a type 2 functional response to T. urticae. The handling time of N. californicus was highest (1.9970 h) against T. urticae nymphs. The attack rate did not change much at 15,30°C, but was significantly higher at 35°C. The handling time decreased significantly with increasing temperature at 15,35°C. At 35°C, the attack rate was highest (0.2087) and the handling time was lowest (0.9511 h). [source] Inducible defences and the paradox of enrichmentOIKOS, Issue 3 2004Matthijs Vos In order to evaluate the effects of inducible defences on community stability and persistence, we analyzed models of bitrophic and tritrophic food chains that incorporate consumer-induced polymorphisms. These models predict that intra-specific heterogeneity in defence levels resolves the paradox of enrichment for a range of top-down effects that affect consumer death rates and for all possible levels of primary productivity. We show analytically that this stability can be understood in terms of differences in handling times on the different prey types. Our predictions still hold when defences also affect consumer attack rates. The predicted stability occurs in both bitrophic and tritrophic food chains. Inducible defences may promote population persistence in tritrophic food chains. Here the minimum densities of cycling populations remain bound away from zero, thus decreasing the risk of population extinctions. However, the reverse can be true for the equivalent bitrophic predator,prey model. This shows that theoretical extrapolations from simple to complex communities should be made with caution. Our results show that inducible defences are among the ecological factors that promote stability in multitrophic communities. [source] Influenza A(H1N1)2009 in the French Pacific territories: assessment of the epidemic wave during the austral winterCLINICAL MICROBIOLOGY AND INFECTION, Issue 4 2010Epidemiological Task Group for Overseas French Territories of the Pacific Clin Microbiol Infect 2010; 16: 304,308 Abstract The three French territories in the Pacific (New Caledonia [NC], French Polynesia [FP] and Wallis and Futuna [WF]) have been affected by an outbreak of influenza A(H1N1)2009 during the austral winter of 2009. This wave of influenza-like illness was characterized by a short duration (approximately 8 weeks) and high attack rates: 16,18% in NC and FP, 28% in Wallis and 38% in Futuna. The number of infected patients requiring hospitalization in critical care services and the number of deaths were, respectively, 21 and 10 in NC and 13 and 7 in FP (none in WF). Diabetes, cardiac and pulmonary diseases, obesity in adults, neuromuscular diseases in children, and Oceanic origin were frequently observed among severe cases and deaths. A significant proportion of the population remains susceptible to A(H1N1)2009, making the occurrence of a second wave likely. A state of preparedness and control efforts must be implemented, based on preventive measures (immunization), as well as combined clinical and virological surveillance and health organization. [source] | |||||||||||||||||||||||||